3rd-Generation (3G) mobile communication is to enable a user to have smooth communication under various conditions, and is to support communication from voice to packet data and from images to multimedia services, which needs a higher data rate, a greater data bandwidth, a higher spectrum utilization rate, higher quality of service and lower power consumption and system cost. Wideband Code Division Multiple Access (WCDMA) is one of mainstream 3G standards, and power control, as one of key WCDMA technologies, is important technical means for solving the problems of near-far effect and self-interference and improving communication quality.
In existing WCDMA, there exists a symbol-level processing method for an uplink DPCCH in a final receiver (RAKE receiver) capable of separating multipath signals and effectively combining energy of the multipath signals. As shown in FIG. 1, the method mainly includes channel estimation, control channel compensation and Maximum Ratio Combining (MRC), Signal to Interference Ratio (SIR) estimation, frequency offset estimation, Transport Format Combination Indicator (TFCI) decoding, DPCCH symbol detection, closed loop diversity, and uplink and downlink power control. The power control has two directions, i.e., uplink and downlink, in the RAKE receiver, wherein uplink power control refers to that a Node B performs channel detection and quality assessment and controls power on the user side to increase and decrease; and the downlink power control refers to that the Node B determines and calculates the increase and decrease of power on the Node B side according to a Transmit Power Command (TPC) symbol, sent by the user, in the DPCCH. When a communication environment is good and signal attenuation and interference are low, transmit power of the user may be decreased by power control while guaranteeing communication quality, thereby reducing interference between users, increasing system capacity and reducing system power consumption; while when the communication environment is poor, the transmit power of the user is increased to enhance strength of a signal and guarantee a good SIR of the signal in the poor environment, thereby guaranteeing communication reliability and quality.
Because of the problems of near-far effect and self interference, the increase of transmit power of a single user may cause influence on quality of service of other users, and then power control has two conflicts in a WCDMA system: increasing the transmit power may improve quality of service and performance of the user on one aspect, and on the other aspect, increasing the transmit power may also increase interference to other users to cause reduction in quality of service and performance of other users.